Here’s one quote from David Cook.

David Cook

David B. Cook is a religious scholar and
author from Rice University in Houston with a focus on Islamic history and
Muslim apocalyptic literature.

“There
is no lack of evidence concerning the Muslim practice of jihad. The classical
and modern works on the subject are voluminous, and they are documented by an
examination of Muslim actions as recorded by historians. There can be no
reasonable doubt that jihad is a major theme running through the entirety of
Muslim civilization and is at least one of the major factors in the astounding
success of the faith of Islam.[39]

“In
reading Muslim literature -- both contemporary and classical -- one can see
that the evidence for the primacy of spiritual jihad is negligible. Today it is
certain that no Muslim, writing in a non-Western language (such as Arabic,
Persian, Urdu), would ever make claims that jihad is primarily nonviolent or
has been superseded by the spiritual jihad. Such claims are made solely by
Western scholars, primarily those who study Sufism and/or work in interfaith
dialogue, and by Muslim apologists who are trying to present Islam in the most
innocuous manner possible.[40]

“...after
surveying the evidence from classical until contemporary times, one must
conclude that today's jihad movements are as legitimate as any that have ever
existed in classical Islam... In short, although the actions of many of these
groups may disgust many Muslims, as far as their conduct of jihad, they fall
within the limits set by classical and contemporary Muslim law.[41]”